Electronic analog bridge type ramp function generators



2, was A. NATHAN 3,264,553

ELECTRONIC ANALOG BRIDGE TYPE RAMP FUNCTION GENERATORS Filed July 15, 1963 G SJGN CHANGWG ADDER LINEAR OR NON-UNEAR N N-UNEP INVENTOR United States Patent 3,264,553 ELECTRONIC ANALOG BRIDGE TYPE RAMP FUNCTION GENERATURS Amos Nathan, Dept. of Electrical Engineering Technion, Israel Inst. Techm, Haifa, Israel Filed July 15, 1963, Ser. No. 294,889 9 Claims. (Cl. 32379) This invention relates to means for rounding off or blunting the break point of the ramp functions produced in electronic bridge type function generators, thereby improving their utility in function generators.

Bridge type function generators of said type are described for example on p. 191 et seq. in R. M. Howe, Design Fundamentals of Analog Computer Components, Van Nostrand, 1961. One use of such function generators is for the production of arbitrary functions. If the break points of said ramp functions are rounded off or blunted, a better approximation to many given functions can thereby be obtained with a given number of ramp functions.

It is the object of the invention to provide means for the rounding off or blunting of ramp functions produced by function generators of the recited type.

The invention will now be more particularly described by way of example in conjunction with the appended drawings in which,

FIGURE 1 is a schematic diagram of an example of a prior art function generator of the type considered;

FIGURES 2 and 3 are plots of ramp functions;

FIGURES 4 and 5 are schematic diagrams relating to examples of functions generators incorporating the improvement of this invention;

FIGURE 6 is a schematic diagram showing how two of the potentiometers in the invention may be ganged;

FIGURE 7 is a schematic diagram of another embodiment of the invention.

The prior art is represented by the example of FIG- URE l which will serve to clarify the terminology used in this specification. Input voltage x is received by the resistive bridge circuit comprising resistors 1 and 2. 7 is a sign-changing adder of unity gain, and 8 is another sign changing adder. The bridge output voltage at terminal 5 is inverted in sign changer 7 and whence combined in adder 8 with the voltage at terminal 6 produces output voltage e at terminal 9. The means establishing the break point comprises break point diode 3 and potentiometer 4. The break point voltage is established by the value of the reference voltage at terminal 10 when diode 3 is off.

For sufliciently small values of x, diode 3 is off, theb ridge is balanced and e =0. For x sufficiently large so that the voltage at terminal 10 is larger than that at terminal 10, break point diode 3 begins to conduct, and, provided that the adjustable contact 10' of poten tiometer 2 is not electrically in its exact centre position, the bridge is unbalanced and e is proportional to x. e is thus represented by the ramp function ABE, FIG- URE 2. Point B is the break point of the ramp function, and x is the effective break point voltage thereof. The slope of the ramp function depends in both sign and magnitude upon the setting of potentiometer 2.

FIGURE 4 is a schematic diagram of one embodiment of the invention as applied to the circuit of FIGURE 1. Components 7, 8 and 9 are not shown in FIGS. 4, 5, 6 and 7 but are electrically connected as in FIG. 1. Nonlinear resistor 11 is connected between the adjustable contact of potentiometer 4 and the cathode of break point diode 3 at terminal 10. Assuming for the moment that diode 12 and potentiometer 13 are not present, the circuit can produce an output voltage e at terminal 9 as shown by ACF in FIGURE 2. For x sufficiently ICC small so that the voltage at terminal 10 is lower than that at terminal 10, diode 3 is not conducting and (2 :0. At x=x or for larger x, diode 3 conducts and 2 depends upon x. Because of the presence of nonlinear resistor 11 the voltage of terminal 10 which is the effective reference voltage is shifted and increases nonlinearly with increasing x. The result is the production of s corresponding to the curved ramp CF, FIGURE 2, for x larger than x This is the simplest embodiment of the invention.

Another embodiment of the invention comprises in addition potentiometer 13 connected to constant potential means at and and diode 12 connected to terminal 10 and to the adjustable contact of potentiometer 13. Potentiometer 13 is so adjusted that the voltage at its adjustable contact is higher than the voltage at terminal 10 when x=x For x smaller than x diodes 3 and 12 are off and e =0, as before. For x larger than x diode 3 conducts and s follows curve C, FIGURE 2. Increasing x still further diode 12 begins to conduct, and the effective reference voltage at terminal 10 is then essentially determined by the setting of potentiometer 13. The produced output ramp function e is as shown in FIGURE 2 by ACE. The invention gradually shifts the effective break point voltage in the break point region of the ramp function from x to x The term break point region denotes that portion of e for which x is in the vicinity of x If potentiometer 13 has small resistance as compared with resistor 11, the ramp at E, FIGURE 2, is substantially linear, but in practice a slight residual curvature occurs and can usually be tolerated. An advantage of the circuit including diode 12 and potentiometer 13 is the fact that the non-linear resistor 11 does not substantially affect e in the ramp region, thus eliminating in this region detrimental effects caused by its temperature dependence, for example. Another ad vantage is the fact that the ramp becomes substantially linear at E.

If resistor 11 in FIGURE 4 is replaced by a linear resistor, e is as shown by ADE, FIGURE 2; i.e. the break point of the ramp is blunted by the straight line D.

Adjustment of potentiometer 13 permits control of the amount of corner rounding or blunting. In particular, if potentiometers 4 and 13 are so adjusted that potentiometer 13 provides a lower voltage than does potentiometer 4, the break point is sharp and an ordinary ramp function is produced, its break point being determined by the setting of potentiometer 13.

In one example the following components and component values are used:

Resistors 1, 2, 250 kilohm Resistors 4, 13, kilohm Input resistance of adders 7, 8, 800 kilohm Resistor 11, having a characteristic given by where V is the voltage in volts and I the current in amperes.

Voltages at +100 volts Voltages at l00 volts Diode 3, vacuum tube diode Diode 12, solid state diode.

FIGURE 5 is a schematic diagram corresponding to FIGURE 4 except for the reversal of the polarity of the diodes. Output e produced thereby is of the type plotted in FIGURE 3, where EBA corresponds to an ordinary v corner, the voltage provided by potentiometer 13 must be lower than that provided by potentiometer 4. The operation of this circuit is analogous to that of the circuit of FIGURE 4.

FIGURE 6 is the schematic diagram of an embodiment of the invention corresponding to that of FIGURE 4, except that resistors 14 and .15 are inserted in series with potentiometers 4 and 13, respectively, and said potentiometers are mechanically ganged, as shown by ganging means 20. The insertion of resistors 14 and 15 ensures that potentiometer 113 provides a higher voltage than does potentiometer 4, when both potentiometers are similar and are set to similar positions. Adjustment of gauging means 20 simultaneously adjusts otentiometers 4 and -13 so that break point round off is substantially independent of the break point setting. If, in addition, adjustment of the amount of round off is desired, this can be achieved by making resistor .14 adjustable, for example.

Another embodiment of the invention is shown in the schematic diagram of FIGURE 7, as applied to the function generator of FIGURE 1. Resistor 16 is inserted between terminal 10 and potentiometer 4. To terminal 10 is connected diode 12 in series with non-linear resistor '11 which is connected to the adjustable contact of potentiometer 18. Potentiorneter 18 is connected to the input terminal receiving voltage x and to constant negative potential means at Non-linear resistor I11 is shunted by adjustable resistor 17. The circuit produces a rounded off ramp function of the type of curve ACE, FIGURE 2, as follows: For x smaller than x diode 3 is off and diode '12 is on, provided that the voltage supplied by potentiometer I18 is adjusted to be sufficiently low. The bridge is thus balanced but the effective reference voltage is lower than that provided by potentiometer 4 because of the voltage drop in resistor 16, from which current is withdrawn through diode 12. This has no effect on 2 because diode 3 is off. For x larger than x diode 3 is on. Raising x decreases the voltage difference between potentiometer 18 and terminal 10, thereby shifting the effective reference voltage at terminal 10 in a non-linear manner. When x=x the voltages at potentiometer 18 and terminal 10 are equal. For x larger than x diode 12 is off and the voltages at terminals 5 and 6 are therefore linear functions of x; therefore e being proportional to their difference, is also a linear function of x. Adjustment of potentiometer 18 and resistor 17 permits control of the amount of break point round off. If resistor 11 is omitted, e corresponds to ADE, FIGURE 2. Inversion of diodes 3 and 12 and replacement of the negative potential at potentiometer 18 by a positive potential adapts the circuit to produce ramps ECA and EDA, FIG- URE 3, with or without non-linear resistor 11, respectively.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What I claim is:

11.'An electronic bridge type ramp function generator for the production of a ramp function voltage for the instantaneous value of an input voltage wherein said ramp function has a rounded off or blunted break point; comprising a ramp function generator of the type recited including input means adapted to receive said input voltage, resistive bridge means connected thereto, reference voltage means adapted to establish the break point of said ramp function, circuit means connected to said reference means, break point diode means connected to said bridge point means and to said circuit means, said circuit means providing a first path connecting said bridge means with said reference means throughsaid diode means; said circuit means including at least one element having a nonlinear current/voltage characteristic and providing a second path passing therethrough from said reference means such that current flow through said non-linear means causes the voltage at said break point diode means to be a non-linear function of said input voltage in the domain of values thereof wherein said break point diode means is conductive.

2. The function generator as claimed in claim 1 including resistive means in said first path connected to said break point diode means.

3. The function generator as claimed in claim 1 wherein said non-linear means includes second diode means providing a path therethrough from said reference means to potential means such that said second diode means changes from conductive to nonconductive state for some predetermined input voltage in said domain.

4. The function generator as claimed in claim 2 wherein said reference voltage means comprises first potential dividing means having an adjustable contact adapted to produce said reference voltage thereat and said resistive means is connected thereto.

5. The function generator as claimed in claim 4 including second potential dividing means having an adjustable contact, said non-linear means includes second diode means connected thereto providing said second path through said second diode means from said reference means to said contact such that said second diode means changes from conductive to nonconductive state for some predetermined input voltage in said domain.

6. The function generator as claimed in claim 5 wherein the voltage provided by said second potential dividing means is constant and said resistive means is non-linear.

7. The function generator as claimed in claim 2 wherein said reference means comprises first potential dividing means having a first adjustable contact, and said resistive means is connected thereto; including second potential dividing means having a second adjustable contact, sec ond diode means connected thereto and to said break point diode means such that said second diode means.

References Cited by the Examiner UNITED STATES PATENTS 2,890,832 6/1959 Stone 235197 2,899,550 8/1959 Meissinger et al. 328-143 3,064,898 11/1962 Walker 235197 3,173,024 3/1965 Peretz 235,-197

OTHER REFERENCES Galli: Control Engineering, Nonideal Diodes and Practical Function Generators, February 1960, pp. 107- JOHN F. COUCH, Primary Examiner.

LLOYD MCCOLLUM, Examiner.

A. D. PELLINEN, Assistant Examiner. 

1. AN ELECTRONIC BRIDGE TYPE RAMP FUCNTION GENERATOR FOR THE PRODUCTION OF A RAMP FUNCTION VOLTAGE FOR THE INSTANTANEOUS VALUE OF AN INPUT VOLTAGE WHEREIN SAID RAMP FUNCTION HAS A ROUNDED OFF OR BLUNTED BREAK POINT; COMPRISING A RAMP FUNCTION GENERATOR OF THE TYPE RECITED INCLUDING INPUT MEANS ADAPTED TO RECEIVE SAID INPUT VOLTAGE, RESISTIVE BRIDGE MEANS CONNECTED THERETO, REFERENCE VOLTAGE MEANS ADAPTED TO ESTABLISH THE BREAK POINT OF SAID RAMP FUNCTION, CIRCUIT MEANS CONNECTED TO SAID REFERENCE MEANS, BREAK POINT DIODE MEANS CONNECTED TO SAID BRIDGE POINT MEANS AND TO SAID CIRCUIT MEANS, SAID CIRCUIT MEANS PROVIDING A FIRST PATH CONNECTING SAID BRIDGE MEANS WITH SAID REFERENCE MEANS THROUGH SAID DIODE MEANS; SAID CIRCUIT MEANS INCLUDING AT LEAST ONE ELEMENT HAVING A NONLINEAR CURRENT/VOLTAGE CHARACTERISTIC AND PROVIDING A SECOND PATH PASSING THERETHROUGH FROM SAID REFERENCE MEANS SUCH THAT CURRENT FLOW THROUGH SAAID NON-LINEAR MEANS CAUSES THE VOLTAGE AT SAID BREAK POINT DIODE MEANS TO BE A NON-LINEAR FUNCTION OF SAID INPUT VOLTAGE IN THE DOMAIN OF VALUES THEREOF WHEREIN SAID BREAK POINT DIODE MEANS IS CONDUCTIVE. 